Jim Mitchell, who helped bring eroticism into the political and social consciousness of San Francisco and later was imprisoned for the sensational killing of his brother, died apparently of a heart attack at his home in western Sonoma County, investigators said Friday.

Paramedics were called to his home near the hamlet of Two Rock on Thursday evening, said Sgt. Mitch Mana of the county coroner's office.

The porn impresario, whose lime-lit life and tragic downfall were featured in a book and television movie, was pronounced dead at around 8 p.m. He was 63.

Mitchell co-founded the Mitchell Brothers O'Farrell Theatre in 1969 with his brother, Artie, and they turned the emporium of eroticism into a recognized city attraction for residents, tourists and even public officials. Many politicians were friends of the brothers, whose sometimes outlandish antics were seen as more charming than troublesome.

But then-Mayor Dianne Feinstein did not see much humor in the peddling of porn. Her attempts to shut the brothers down came to a head when her unlisted phone number was placed on the theater marquee with the words "For a Good Time, Call ..."

The shooting of Artie Mitchell in 1991 hit San Francisco like a bolt of lightning, signaling the downfall of not just a family but of an era forged during the sexual revolution. To many, the death of Jim Mitchell marks the final chapter of that saga.

"How sad. I know he had enemies, but he had friends, too. I was one of them," said Terence Hallinan, the former San Francisco district attorney who acted as the brothers' private attorney. "He was a guy who had a lot of tensions, a lot of pressure on him. ... The thing with his brother, right or wrong, that is something you are never going to live down with yourself."

James Lloyd Mitchell grew up in Antioch, then a hardscrabble mill town. He and his brother often called themselves Okies because their parents were products of the Dust Bowl migration into California.

The brothers looked alike and were always very close, according to relatives. They both served in the Army, briefly attended local colleges and had failed marriages.

Jim was more subdued and serious, while Artie was known as outgoing, a prankster, but the two did almost everything together.

On July 4, 1969, the brothers opened the O'Farrell Theatre, a large, dark series of rooms, stages and booths with mirrors and nude and semi-nude women performing a melange of sexual acts. In a gesture toward San Francisco environmentalists, the outside walls were covered with murals of whales.

They produced a string of pornographic movies, including "Behind the Green Door," featuring Marilyn Chambers, in 1972. The flick, which cost $60,000 to produce, was one of the first porn films with a plot line, but it hit it big when it was learned that Chambers also had worked as a model for Ivory Soap.

The brothers took great joy in tweaking Feinstein and the establishment.

Former Chronicle columnist Warren Hinckle said he became great friends with the brothers after castigating the police in his column for a raid in which Marilyn Chambers was arrested.

"Feinstein couldn't stand the idea that this huge, highly successful, very elaborate old-fashioned San Francisco burlesque show was operating downtown, so she launched a vendetta," Hinckle said. "They arrested me for walking my dog without a leash because I was making fun of them for using 30 cops to arrest one naked woman. All of a sudden, I was in the soup, too, and we became fast friends."

The brothers were constantly in court, spending much of their fortune successfully arguing that they had a First Amendment right to entertain people the way they saw fit. They also helped support underground artists, including Robert Crumb of Zap Comix fame, Hinckle said.

The brothers made influential friends, including former Mayor Frank Jordan, Sheriff Michael Hennessey and former Police Chief Richard Hongisto. The late author Hunter Thompson spent two years hanging around the theater as "night manager," working on a book that was never finished.

Their glory days came to an end on Feb. 27, 1991, when Jim Mitchell kicked in the door of his brother's Corte Madera home and shot him to death. He was carrying a pistol, and stuffed down his right pants leg was a .22-caliber Winchester rifle, when police arrested him.

The highly publicized trial that followed was both gripping and heartbreaking. Prosecutors argued that Jim had become increasingly angered by his brother's alcoholism and planned the killing. The defense called the killing "intervention gone awry."

The jury concluded that the killing was voluntary manslaughter committed by the elder brother in the heat of passion. Mitchell was released from San Quentin Prison on Oct. 3, 1997, after serving less than three years for his brother's slaying.

Artie Mitchell's six children filed wrongful death suits against their uncle, which later were consolidated and settled out of court. But the wounds never healed.

In 1997, one of his nieces, Mariah Bradford, broke years of silence to criticize her uncle.

"If it were an accident, I would expect a lot of remorse," she told The Chronicle. " 'How can I make it up to you?' I would expect an apology. We never had one -- not even an attempt."

Mitchell apparently spent the last years of his life riding and caring for horses.

In 2000, a Showtime movie called "Rated X" recounted the tale for a national audience. Charlie Sheen played Artie, and Emilio Estevez, who also directed the movie, played Jim.

The brothers' theater was still operating Friday. Frankie Zee paid $20 to get in, a price that included a free lap-dance token. Zee, who has been going to the theater since 1975, said Mitchell would be remembered for creating a special theater full of special women.

Outside, the theater was showing its age. Its fabled blue whale and fish mural was fading and, in spots, was decorated with graffiti, a relic of a movement, a time and a political attitude that might have finally passed on Friday.

"They were a part of the counterculture," Hinckle said of the Mitchell brothers. "Jimmy was a pioneer, a champion and one of the funniest guys you will meet. He was one of the great guys in the great tradition of tough old San Francisco, maybe the last one of them."